1. Field of the Invention
This invention relates to a solid-state laser, and particularly to a solid-state laser including an etalon, incorporated in a resonator, to make a single longitudinal mode of oscillation in the width of the oscillation wavelength of the medium of the laser.
2. Description of the Prior Art
A laser diode pumping solid-state laser has already been known from, for instance, U.S. Pat. Nos. 4,656,635 and 4,701,929 in which a solid-state laser rod, which is doped with rare earth material such as neodymium, is pumped by a semiconductor laser (laser diode). In this type of solid-state laser, in order to suppress noise due to the mode competition, an etalon is disposed inside the resonator to achieve a single longitudinal mode of oscillation.
However, it has been hitherto admitted that the use of the etalon inside the cavity resonator, in such a manner as mentioned above, involves a considerable amount of increase in the threshold value of a pump power for the oscillation of a solid-state laser, thereby resulting in a drop in the output of the solid-state laser. The increase in the threshold value is attributed to the fact that the interval of longitudinal modes of an etalon is set to be large enough to make only one longitudinal mode of oscillation in the width of the oscillation wavelength of a solid-state laser medium.